this just my 5cent la. my suggestion only.
try buid up strong fire team.
leader = fire grim reaper. nice 2 aoe skill, and extra 1 turn if u kill an mobs. leader skill is + ally fire mobs 30% atk power.
buffer = hellhund. very good in ++ whole team
attacker = sure is fire inugami. combo with hellbound buff, u will get an monster.
healer = sure is fire priest. she may not the best healer, but she can be strong if u put the right runes.
support = fire mystic witch. she skill very good also, remove all weakening effect on whole team and also ++ HP, minimun of 10% HP.
when enermy put a boom at ur whole team head, or whole team got 2 3 4 weakening effect to make ur team weak, (this always happen in dungeons)
then u will feel the important of removing weakening effect skill
ur idea looks good. i think i will try to push reaper and witch to max 4* (if possible awaken too) and see how the team goes from there. hehe